Answer :
6r + 7 = 13 + 7r
subtract 6r from both sides...
7 = 13 + r
subtract 13 from both sides...
-6 = r
r = -6
subtract 6r from both sides...
7 = 13 + r
subtract 13 from both sides...
-6 = r
r = -6
[tex]6r+7=13+7r\ \ \ \ | subtract\ 6r\\\\
7=13+r\ \ \ \ | subtract\ 13\ \ \ \\\\
-6=r\\\\Solution\ is\ r=-6.[/tex]